Building block



FIG. 1 is a front view of the first, second, third and fourth embodiments of a building block showing my new design;

FIG. 2 is a side elevational view of either side of the first embodiment thereof;

FIG. 3 is a plan view of the first embodiment thereof;

FIG. 4 is a perspective view of the first embodiment thereof;

FIG. 5 is a plan view of the second embodiment thereof;

FIG. 6 is a side elevational view of either side of the second embodiment thereof;

FIG. 7 is a plan view of the third embodiment thereof;

FIG. 8 is a side elevational view of either side of the third embodiment thereof;

FIG. 9 is a plan view of the fourth embodiment thereof;

FIG. 10 is a side elevational view of either side of the fourth embodiment thereof; and

FIG. 11 is a rear view of each of the embodiments thereof. 

The ornamental design for a building block, substantially as shown and described. 